The control of approaching and departing aircraft at busy airports by air traffic controllers is a stressful occupation involving what some persons might categorize as an unusual mixture of tools and techniques. On one hand, controllers have the use of very sophisticated radar systems and computers to keep track of thousands of aircraft at any one time. On the other hand, controllers are forced to use what might be called almost primitive systems of handling data with regard to individual aircraft, including the manual passing of small strips of paper from one controller to another when the responsibility for a given aircraft is being transferred. Too, each air traffic controller in a busy airport is often required to monitor dozens of arriving and departing flights on a radar screen in the tower. Currently, each aircraft that comes into a controlled area is represented on a flight progress strip--a piece of stiff paper essentially 3/4 inch high by 8 inches wide, which is slipped into a narrow plastic holder to facilitate manual handling by controllers. On each strip is printed the aircraft identification (e.g., American Airlines flight No. 1246), the aircraft type (e.g., a Boeing 747), the departure and arrival airports and any en route airports that serve as waypoints, departure time (in local time), Federal Aviation Administration (abbreviated FAA) region, etc.
All of the printed information on a flight progress strip is actually printed in a local tower--based upon information that comes on telephone lines from one of 20 mainframe computers in the U.S. These mainframe computers are referred to as flight data input/output computers, which would properly be abbreviated as "FDIO." However, a commonly used colloquialism for referring to these interconnected (and redundant) computers is "FIDO." In one sense, the collective FIDO computers may be thought of as the "mother of all great computers," because they have so much stored information about all kinds of aircraft (including their dimensions, normal weights, nominal cruising speeds, etc.), the locations of airports throughout the world, etc. So when an airline or pilot files a flight plan in Boston, announcing an intention to fly to Dallas, FIDO can cause a flight progress strip to be printed in the control tower in Dallas--well before the air traffic controller will ever make radio contact with the incoming pilot.
When a given flight progress strip has been printed in a local airport, someone (typically the clearance delivery operator) will tear off the strip and insert it into a narrow plastic sleeve, so that it can be manually handled with ease. The sleeve has an open front so that an air traffic controller will later be able to write certain information on the face of the printed strip with a pen; written information on the face of the strip will typically be the radio frequency over which communication will be established between the controller and the pilot, the runway that the aircraft is expected to land on, gate information, etc. For a departing aircraft, hand-written information added to a printed flight progress strip may include the planned takeoff direction, the altitude that the pilot is expected to reach when leaving the airport's controlled airspace, etc. When a controller is monitoring several aircraft, the plastic holders are arranged on an inclined rack in front of the controller's work station. A typical rack may hold as many as 36 plastic sleeves, arranged in two columns of 18 each in front of the controller. When a given aircraft has taken off and it is no longer the responsibility of a particular controller, the sleeve for that particular aircraft is manually pulled off the rack, the strip is pulled out of the sleeve and deposited in the supervisor's "archives" space, and the empty plastic sleeve is dropped into a bin for reuse.
In the event that an aircraft has departed a gate on one side of a major airport, but the aircraft is expected to take off on a runway on the other side of the airport, logic dictates that the aircraft be "passed-off" to a controller whose work station is on the other side of the tower. This is presently accomplished by having the first controller pick up the plastic sleeve for this particular aircraft from his or her rack and physically hand it to a controller on the other side of the tower. The receiving controller then places the plastic sleeve among those which are already on his/her rack, and responsibility for the aircraft has thereby been officially "transferred." Unfortunately, the somewhat primitive nature of this practice of transferring responsibility for aircraft in a control tower is susceptible to accidental error. Strips can be misplaced or even "lost" if they fall to the floor and are not observed by a controller, etc. In fact, the official FAA report of the crash that occurred in Los Angeles on Feb. 1, 1991 (in which an incoming Boeing 727 landed on top of a smaller commuter aircraft that was getting ready to take off) was attributed--in part--to misplacement of a flight progress strip in the airport tower. According to the Aircraft Accident Report, NTSB/AAR-91/08, PB91-910409 dated Oct. 22, 1991, one of the causes of the Los Angeles runway collision was that the clearance delivery operator in the tower did not follow the rules and pass a particular strip to a certain ground controller. The local controller subsequently had an incorrect perception of the traffic situation on the ground, and gave clearance to the larger aircraft to land; it eventually landed on top of the departing commuter aircraft--an aircraft whose flight progress strip had been "misplaced" in the tower.
Another situation can arise when a TRACON operation (which is involved in the tracking of airplanes by radar, from take off to a point that is fifty miles out) is moved so that it is no longer within convenient "hand-off" distance from one person to another. For example, at Chicago's O'Hare airport, the TRACON function has been accomplished for many years in the basement of the control tower; but plans are well under way to transfer that function to a facility that is several miles away--in Elgin, Ill. As long as multiple functions were concentrated in one building, a flight controller simply pulled a flight progress strip out of its plastic holder and dropped the strip down an open shaft that led to the basement, much like dirty linen in a hotel is frequently dispatched to the basement for washing. To deal with the new logistics of having TRACON people located miles from the control tower, it has been suggested by some officials that facsimile machines be used to get data on departing planes from the tower to the TRACON facility. Of course, critics of such a plan might point out that passing flight information via outgoing and incoming FAX machines is not necessarily the best way of preserving the quality of hard copy, nor is it likely to be productive in terms of efficient use of man hours, etc. FAX-to-FAX communication also reintroduces the possibility of the information associated with a given strip being lost while it is in transit from a controller to the TRACON facility.
While the management of thousands of aircraft in the air over the U.S. at any given time may be perceived as being in need of modernization, this is not to say that there haven't been persons who have given their attention to making air travel even safer than it is. In particular, there are those who have given attention to possible ways of removing some of the stress from air traffic controllers by using modem technology. Among some of the more significant proposals are those found in U.S. Pat. No. 4,827,418 to Gerstenfeld entitled "Expert System for Air Traffic Controller Training"; U.S. Pat. No. 4,890,232 to Mundra entitled "Display Aid for Air Traffic Controllers"; U.S. Pat. No. 5,181,027 to Shafer entitled "Method and Apparatus for an Air Traffic Control System"; and U.S. Pat. No. 5,200,902 to Pilley entitled "Airport Control/Management System." But in spite of the suggestions in these patents, there has remained a need for improvement in the way that air traffic controllers do their work in the control towers at major airports; and it is an object of this invention to provide a system that will satisfy this need.
Another object is to increase the capabilities of air traffic controllers by increasing the information that they may selectively call up from various data files that are, or could be, tied in with their computers.
A further object is to increase the ease with which an archival record may be created of work in a control tower, so that training of new controllers might be enhanced by permitting them to observe real situations at speeds that are slower than they happen in real time.
One more object is to provide a system for monitoring the takeoff and landing of aircraft at a busy airport, which system offers improved safety factors for all concerned.
These and other objects will be apparent from a careful reading of this specification and the claims appended thereto, as well as reference to the several figures of the drawing attached hereto.